Our guest blogger is Andrew Light, a Senior Fellow at the Center for American Progress, who is now attending the United Nations climate change talks in Poznań, Poland. This is the fifth of several on-the-scene dispatches.

In front of a capacity crowd in the largest hall available at this year’s UN climate change conference, Al Gore gave a dramatic address on the possibilities and the hurdles before the climate change community. The biggest, longest applause line by far (complete with hoots and whoops) went to his indirect endorsement of Bill McKibben’s 350 campaign inaugurated on the instigation of an argument first floated by NASA’s James Hansen in a paper released shortly after last year’s UN climate change meeting in Bali. According to Hansen, “We need to reduce from today’s atmospheric CO2, about 385 parts per million, to 350ppm. We are already too high to maintain the climate to which humanity, wildlife, and the rest of the biosphere are adapted. (. . .) This target must be pursued on a timescale of decades.”

Though Gore did not mention the campaign by name the concept was clear:

The truth is that the goals we are reaching toward are incredibly difficult. Even [a stabilization of atmospheric CO2 at] 450 ppm is inadequate. We need to make that goal 350ppm. (. . .) This task can seem daunting. For those of us who understand the goal should be tougher let us understand that the early steps in the process to go from 450 to 350 are very familiar. Once processes of change begin, once decisions are arrived at, then the task becomes easier in the doing. We will see that as we start changing we will improve our economies and increase our standard of living.

Watch it:

The atmosphere in Poznań for Gore’s speech was less dramatic than that surrounding his address at last year’s UN climate change meeting in Bali, though in some ways his task this time around was more difficult. Rather than confronting Bush’s intransigence against a unified world community, Gore had to contend with a depressing malaise that has pervaded the halls of the conference and haunted delegates and observers as they trudged through the cold, cloudy and wet weather on their way to the venue. There was also plenty of blame to go around this time, with accusations hurdled between developed and developing countries of who was responsible for the lack of progress.

Whether he knew this or not, it was good that Gore focused on his reasons for optimism. These included the emerging consensus that a green stimulus and recovery package was the best way to put people to work (a focus of CAP’s efforts on climate and energy), progress in China on similar initiatives, new research in green energy, and several signs of hope in the United States. (The biggest laugh was Gore’s mention of the Supreme Court’s ruling in Massachusetts vs. EPA, which he prefaced by saying, “I must tell you, in my opinion, the Supreme Court does not always reach the right decision.”)

Reminding the crowd of his plea in Bali, Gore mentioned his meeting with President-elect Obama before coming here. Of that conversation Gore said that Obama had emphasized “that the climate crisis would be a top priority and the US will once again engage vigorously in these negotiations,” garnering the second most sustained applause.

Several hours later in a session featuring McKibben and Bianca Jagger the 350.org people were more charged up than any group so far at this meeting. McKibben’s opener:

That was an important moment for us and for this entire debate. A year ago nobody knew that number. Jim Hansen hadn’t said it yet. Today Al Gore moved it up another notch.

Also before a standing room only crowd (though in a smaller room) McKibben proclaimed that we now have the world’s leading scientific authority on climate change – Hansen – and the world’s leading political authority on climate change saying the same thing. “There is no longer any question that this is where the target is set.” If the numbers stick, according to McKibben, citizens can ask their elected representatives one simple question as each complicated CO2 reduction plan is floated: “Does this plan you have given us get us to 350 or not?”

The chief focus of 350.org is an international day of awareness and protest scheduled for October 24, 2009 where they ask for everyone concerned with global warming, regardless of the depth of the weeds of policy making they choose to wade into, to also do something “incredible, radical, or sexy” to highlight the importance of this number.

Does this endorsement entail a commitment from Gore’s massively financed Alliance for Climate Protection to support impoverished, according to the pleas made at this meeting, 350.org? So far there does not appear to be anything formally in the works. In an interview with one of McKibben’s assistants, while it was acknowledged that “Al and Bill” talk often, and are fond of one another, word of resources behind McKibben’s efforts, which he says will be disbanded after the October 24th day of action, are still up in the air.